Since 1966, the Cholera Research Laboratory has been collecting demographic data in the Matlab, a rural area in Bangladesh. There have been four censuses; registration of births, deaths, and migrations has been accomplished by daily visits to households in the area. The accumulated data provide a valuable record of demographic movements in an under-developed country over a period of some ten years. The data have been key-punched, but have not been systematically edited for redundancies, omissions, and errors. Because both record formats and identifying information have changed over the years, it has been extremely difficult to use the data for other than routine demographic purposes in the past. All data collected from May 1966 through April 1976, except the 1966 census, are now available on magnetic tape at Johns Hopkins. The objectives of this study are to "clean" and organize the data, to prepare a report analyzing the data collected in the first ten years, and to establish procedures for data processing in the future. We envision a completely linked file, suitable for retrospective studies and for use as a sampling frame for prospective studies, both in demographic and in epidemiologic research.